Process of devulcanizing vulcanized india-rubber scrap.



UNITED STATES PATENT OFFICE.

GEORGE EDWARD I-IEYL-DIA, OF WARRINGTON, ENGLAND.

PROCESS OF DEVULCANlZING VULCANlZED INDIA-RUBBER SCRAP.

$PEQIFICATION forming part of Letters Patent No. 689,616, dated December24, 1901. Application filed June 11,1901. Serial No. 64,188. (N pimens.)

To all whom it may concern.-

Beitknown that I, GEORGE EDWARD HEYL- DIA, engineer, a subject of theKing of Great Britain, residingin Warrington, in the county ofLancaster, England, (whose full postal address is Birk Crag, 286 GreatClowes street, Higher Broughton, Manchester, in the county of Lancaster,England,) have invented certain new and useful Improvements in Processesof DevnlcanizingVulcanized India-Rubber Scrap, of which the following isa specification.

This invention has for its Object the devulcanization of ordinaryvulcanized rubber, more especially scrap.

The rubber, preferably cut up into small pieces, is first submitted inan iron or other suitably-closed tank to the action of solventssuch asnaphtha, benzol, spirits of turpentine, or other suitable solventscapable of dissolving sulfur, but not of dissolving india-rubber at theheat employed. The tank'is heated, but to a heat not exceeding thevolatilizingpoint of the respective solvents at the pressure used andnot exceeding 120 Fahrenheit. In order to prevent the pressure in thevessel rising to too great a degree,a stand-pipe cooled by water andconnected with the upper portion is connected to the vessel, so that thesolvent-vapors rising from the mixture are con-' densed and run backinto the tank. The result of this working is that the bulk of the sulfurcontained in the vulcanized rubber is dissolved out into the solvent,while the rubber remains'practically untouched, the temperature beingtoo low to dissolve the rubber. 1

After the digesting process has been carried on for several hours thesolvent is drawn off from the tank and submitted to a distillingprocess, when the solvent is recovered, and the sulfur remains in theretort as solid crystals. If the rubber be not entirely devulcan ized, afresh batch of solvent is admitted to the tank. It is obvious that thetank can be of any length, and if a long narrow tank be used'I may makea continuous process of it by drawing thesolvent from one end,distillingit, and sending the vapors or the distilled solvent back into the tankat the other end, the rubber being passed through the tank in thereverse direction and removed from time to time at one end, while freshrubber is added at the other.

The devulcanized rubber formed in the above manner is suitable forspreading or for other purposes' If a continuous process be not used,the devulcauized material while still remaining in the tank is coveredwith fresh solvent and the tank then exposed to heat not exceeding 350Fahrenheit and pressure preferably not exceeding forty five pounds-onthe square inch, and by this means a solution of india-rubber isobtained. This solution can be used as it is, or it may be dried in thefollowing manner, so as to be worked up again into a solid-rubber sheet:A temperatu re considerably above the volatilizable point of the solventused is applied, and the result is that the solvent is slowly distilledoverand is condensed in a condenser for reuse. WVhen the dissolvedindia-rubber has been brought down to a soft plastic state, it will befound impracticable to continue the distillation any further except byincreasing the heat to such a degree as would destroy orinj ure theindia-rubber. When therefore the material arrives at thesoft plasticstate, it is passed to a closed kneading-machine, where it is kneadedwith hot water, the water being kept at a boiling temperature, or at anyrate sufiicientlyhot to evaporate the solvent. The rubber is thus leftbehind without a trace of solvent. It is taken out, dried, and is readyfor use.

I declare that what I laim is 1. The process of obtaining ordinaryindiarubber from vulcanized rubber, which consists in cutting up thevulcanized rubber into small pieces, heating it with a solvent of sulfursuch as described, at or about the volatilizable point of the solventuntil the sulfuris dissolved out but maintaining the solvent in a liquidstate throughout the heating, drawing off the solvent, treating theindia-rubber in a similar Way with further solvents until all the sulfuris dissolved out, and distilling the solvent separately, wherebysolvents for reuse and sulfur, are obtained in separate forms. 3

2. The improvement in the process of devulcanizing india-rubber, whichconsists in heating the same with such solvent of sulfur as will not atthe heat used dissolve the indiarubber, the solvent being maintained ina l kneading the remainder with hot water in a liquid state throughoutthe heating.

3. The improvement in the process of obtaining india-rubberfromvnlcanized indiarubber scrap, which consists in dissolving out thesulfur by means of a solvent and heat at a temperature not exceeding 120Fahrenheit, separating the liquid from the india-rubber and dissolvingthe recovered rubber in fresh solvent, whereby a solution ofunvulcanized india-rubber is obtained.

4. The improvement in the process of ob raining solid unvnlcanizedindia-rubber from devulcanized india-rubber scrap, which consists inseparating the sulfur from the vulcanized scrap by means of solvents andheat, dissolving the purified rubber in fresh solvent distilling off aportion of the solvent, and then closed chamber, whereby the remainingsolvent is evaporated and can be condensed.

5. The improvement in the process of treating a solution of india-rubberfor obtaining a solid therefrom, which consists in slowly distilling thesame until it arrives in the soft plastic state, and. then kneading thesame in hot water, whereby the remaining solvent is driven olf, and thendrying, substantially as described.

In witness whereof I have hereunto signed my name, this 31st day of May,1901, in the presence of two subscribing witnesses.

GEORGE EDWARD HEYL-DIA.

Witnesses:

AUSTIN W. MEDLEY, SIDNEY W. D01).

